Process for preparing polysiloxanes



United States Patent PROCESS FOR PREPARING POLYSILOXANES George H.Wagner, Clarence, N. Y., and Charles E. Erickson, New Brunswick, N. J.,assignors to Union Carbide Corporation, a corporation of New York NoDrawing. Application April 25, 1955 Serial No. 503,779

2 Claims. (Cl. 23-14) This invention relates to a process for theanhydrous condensation of substituted silanes, to form polysiloxanes.More particularly, the invention relates to a process for preparingpolysiloxanes which comprises heating a substituted silane, containingonly hydrogen, chlorine and alkoxy groups bonded to the silicon atomthereof, in the presence of a catalyst, to its boiling temperature.

The starting materials employed in the present invention are substitutedsilanes which can be represented graphically by the formula:

where R represents an alkyl group, such as methyl, ethyl,

propyl and the like groups, while Y represents either 3 a chlorine atomor an alkoxy group. Thus our starting materials include.dialkoxychlorosilane and alkoxydichlorosilane.

In accordance with our invention the polysiloxanes are prepared byheating a substituted silane containing only hydrogen, chlorine andalkoxy groups bonded to the silicon atom thereof, in the presence ofaluminum or boron trichloride, to its boiling temperature. The reactionmay be depicted by the following equations where dialkoxychlorosilane isemployed as the starting material in one instance and wherealkoxydichlorosilane is the starting material in the other:

The process may be carried out by placing a substituted silane, such asalkoxydichlorosilane and a catalyst, such as aluminum chloride, in aflask connected to a reflux column and heating the mixture to itsboiling temperature under reflux conditions. An alkylchloride is evolvedand heating is continued until evolution ceases. The product is apolysiloxane containing hydrogen and chlorine atoms bonded to thesilicon atoms thereof.

Example I To a 100 cc. of HSi(OEt) Cl was added 0.1 g. of

Patented July 22, 1958 "ice A101 and the mixture was heated to reflux(about C.) for 2 hours. Ethyl chloride and ethyl ether were evolvedduring the refluxing, and a white solid was formed which was found, byanalyses for H, Si and C, to have essentially the empirical formula[HSiO The present application is a continuation-in-part application ofour copending application Serial No. 106,972, filed July 26, 1949, nowPatent No. 2,731,485.

What is claimed is:

1. A process for preparing hydrogen-containing polysiloxanes whichcomprises heating substituted silanes of the type:

where R is an alkyl radical and Y is a radical taken from the groupconsisting of chlorine atoms and alkoxy groups, in the presence of acatalyst taken from the group consisting of the chlorides of aluminumand boron to its boiling temperature under reflux conditions and when "Yis a chlorine atom recovering a siloxane polymer having the repeatingunit:

[HSiOCl] References Cited in the file of this patent UNITED STATESPATENTS 2,458,703 Hatcher Jan. 11, 1949 2,485,928 Servais Oct. 25, 19492,559,167 Myers July 3, 1951 2,618,646 Hatcher et al. Nov. 18, 1952FOREIGN PATENTS 476,174 Belgium Oct. 31, 1947 478,117 Belgium Jan. 31,1948 OTHER REFERENCES Calingaert: Jour. Am. Chem. Soc., vol. 62 (1940),pages 1107-1110.

1. A PROCESS FOR PREPARING HYDROGEN-CONTAINING POLYSILOXANES WHICHCOMPRISES HEATING SUBSTITUTED SILANES OF THE TYPE: